Pyrrole dyes



Patented Oct. 22, 1946 PYRROLE DYEs Leslie (l.` S. Brooker and Robert H. Sprague, Rochester, N. Y., assignors to Eastman Kodak Company, Rochester, N. Y., a corporation of New Jersey Application August 15, 1941, Serial No. 407,033

In Great Britain February 17, 1939 i This invention relates to improvements in photographic elements and more particularly in photographic elements having light screening substances therein. Y

This application is a continuation in part of our application Serial No. 317,726, filed February 7, 1940. It is known that photographic elements require, for many purposes, to have light screening substances incorporated therein. Such alight screen substance may be in a layer overlying a light sensitive emulsion or overlying two or more light sensitive emulsions; or it may be in a light sensitive emulsion for the purpose of modifying a light record in such emulsion or of protecting an underlying light sensitive emulsion or emulsions from the action of light of wave length absorbed by such light screening substance; or it may be in a layer not containing a light sensitive substance `y-but arranged between two light sensitive emulsions; or it may be in a layer serving as a backing on an element having one or more light sensitive emulsions (for example, to reduce halation).

In particular, light screen substances are often required (a) in overcoatings upon photographic elements to protect the light sensitive emulsion or emulsions from the action of light which it is not desired to record, e. g. vultra-violet light in the case of still or moving pictures, especially color pictures, (b) in layers arranged between differentially eolor-sensitized emulsions, e. g. to

Vprotect redand green-sensitized emulsions from the action of blue light and (c) in backings forming the so-called anti-halation layers, on either side of a transparent support carrying the lightsensitive emulsion or emulsions.

In most cases, and especially when the element contains a color-sensitized emulsion or color-sensitized emulsions, it is particularly desirable to employ light-screening substances which do not affect the general sensitivity or the color sensitivity of light-sensitive emulsions with which they may come into contact. It is also particularly desirable to employ light-screening substances which do not substantially diffuse from the layers or coatings in which they are incorporated, either during the manufacture of the element or on keeping it or in photographically processing it. Finally, it is generally necessary to employ light-screening substances which can readily be rendered ineffective, i. e. decolorized or destroyed and removed, prior to or during or after photographic processing; for many purposes it is particularly convenient to employ light-screening substances-which are rendered inployed in processing the element after exposure, e. g. a photographic developing bath or fixing bath or a silver-oxidizing (including silver-removing) bath. For example, in an element which is to be processed by reversal, it is often convenient to employ a light-screening substance which is rendered ineffective by the developer employed to develop the latent image or images to silver since exposure to light of the residual light sensitive emulsion or emulsions may thereby be facilitated. This is particularly the case when, in making color photographs, several differentially color-sensitized emulsions, constituted, for example, by silver halide, such as silver bromide dispersed in gelatin, collodion or other colloid, are coated on one or both sides of a support, for example in inseparably-superimposed layers. Such differentially color-sensitized emulsions have to be processed to different colors and to facilitate the differential colorprocessing,meth ods involving selective exposure of light sensitive images in the layers may be employed. Such selective re-exposure, e. g. of silverhalide remain.- ing undeveloped in development of the latent images formed in silver halide emulsion layers (residual silver halide) is often facilitated if the light-screening substance which was present during the original exposure is decolorised or removed in the developing bath employed to develop the latent images to silver. Any of the elements referred to above may be such that one or more of the emulsions contain coupling components, e. g. those described in French Patent 834,371, granted August 16, 1938.

Numerous substances have been employed as light-screening substances for the purposes indicated above. Many of these are known yellow dyes but it has proved extremely difficult to rlnd dyes having the combination of qualities desired. Many are not resistant to diffusion and Wander rather freely from the layer in which it is intended that they should remain; many adversely affect the sensitivity of light sensitive emulsions with which they come into contact (a number of these reduce the general sensitivity or some specific color sensitivity thereof, but others of them may even impart an additional and unwanted specific color sensitivity thereto) We have now found a class of dyes, members of which fulfill toa very satisfactory extent the requirements of light-screening substances for use in photographic elements. This class consists of polymethine dyes derived from pyrrole or indole or from their substituted` derivatives.`

Such dyes may have a pyrrole nucleus or an indole nucleus (in either case containing substituents or not) linked to a heterocyclic nucleus containing a nitrogen atom either directly or through an intermediate polymethine chain so that in either case there is a chain, comprising an odd number of carbon atoms having conjugated double linkages between the nitrogen atoms.

In the drawing, the gures are enlarged sectional views of photographic elements showing overcoating, lter, and halation layers according to our invention.

The compounds which we propose to use as screening dyes have the following general formula:

where Z=the non-metallic atoms necessary to complete a heterocyclic nucleus J :the non-metallic atoms necessary to complete a pyrrole nucleus R=hydrogen, alkyl, or a chemical bond of a pyridine ring R=hydrogen, alkyl, aryl, or a chemical bond of the same pyridine ring as R d=2 or 3 n=1 or 2 X=an acid radical The general formula indicates that the compounds may be depicted in two electromeric (S-ethyl-Z-benzoxazole) (l-methyl--pyrrole)-dimethinecyanine `iodide 2.2 g. (1 mol.) 2--acetanilldovinylbenzoxazole ethiodide, 2.4 g. (l mobi-500%) N-methylpyrrole and cc. acetic anhydride were boiled 7 minutes with stirring in a test tube. Dye separated from the boiling mixture. Chilled, filtered, washed with acetic anhydride and acetone and dried. Yield 1.7 g. The product appeared to be a mixture of unchanged starting material and the desired dye. The dye was obtained fairly pure by chilling the solution of the crude product in 50 cc. abs. EtOH for 30 minutes, whereupon the dye separated as red crystals. The mixture was ltered as soon as yellow crystals started to separate. Yield 5 g., 26% M. P. 264-266\ with decomposition. After a further recrystallization from abs. EtOH, (100 cc./g.) the product was obtained as red crystals melting with decomposition at 265-267".

EXAMPLE 2 \c-CH=CH \N% om H CH@ ce N/ (3-ethy12-benzoxazole)(l-lauryI-2,-dimethyl-3-pyrrole)-dimethine cyanine iodide 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 5.26 g. (1 mobi-100%) 1lauryl2,5dimethylpyrrole and 20 cc. of acetic anhydride were reuxed 10 minutes. The orange reaction mixture was chilled, product ltered off, washed with acetone and water and dried. Yield 4.4 g., '78%. After recrystallization from abs. EtOH, (10 cc./ g.) the product was obtained as orange crystals melting with decomposition at 20G-207. Yield 3.7 g., 66%.

1 -Zauryl- 2,5 -dimethylpyrrole Prepared by the method of Lions et al. Proc. Royal Soc., New South Wales, 1937, 71, 92 from laurylamine. B. P. 152-155/2 mm. Yield 75%.

1-lauryZ-Z,5-dimethyZ-3-pyrrole aldehyde CHaN-CHa CHz(CHz)wCHa 1.75 g. (1 mol.) 2-methylbenzothiazole-eth0-ptoluene-sulfonate, 1.46 g. (1 mol.) 1laury1-2,5 dimethyl-S-pyrrole aldehyde and 10 cc. of acetic anhydride were reuxed in 5 minutes. The 0range reaction mixture was chilled, diluted with 50 cc. of ether and the product filtered off. The red crystals were washed with acetone and water and dried. Yield 1.5 g., 48%. After recrystallization from abs. EtOH, (28 cc./g.) the product was obtained as Vermillion crystals melting with decomposition at 18l-182.

EXAMPLE 4 dim@thinecyanine-p-toluonesulfonate 3.3 g. (1 mol.) quinaldine metho-p-toluenelpyrrole..aldehyde,4 dropsof -piperidine and15 oc.

` of absolute EtOHwi/ere` reiiuxed 110 minutes. @The :orange solution was cooled, diluted. to 300 cc.swith ether .and chilled. rThe dye wasliilteredv off, washed with water and acetone and dried. Yield 5.2 g., 87%. .After recrystallization from. abs.

V.EtOHy (12 cc./g.) .ftheproduct` was obtained as red '.crystals s melting with decomposition at '163- 1.165". "Yield 3.4 g.; 57%.

EXAMPLE 5 3[ (3-ethyl-2 (3) -benzoxazolylidene) ethylidene] 2- methyl-indolenine hydro-iodide 2.2 g. (lmol.) 2-/8acetanilidovinylbenzoxazole ethiodide,.2.6 g. (1 mol.-|100%) a-methylindole `and cc..of acetic anhydride were boiled minutes in atest tube. Dyeseparated-rom the boil-4 ing solution. Chilled, filtered, washed with water and acetone and dried. Yield 1.4 g., 65%. After recrystallization `from MeOI-I, (120 cc./g.) the product was obtained as brown needleswith metallic reflex melting with decomposition `at 287-288". f Yield 1.25 g.,58%.

3[(3-ethyl-2(3)benzothiazolylidene)' etliylidenel-Z-methylindolenine hydro-iodide 2.25 g. (1 n1ol.)f` 2--acetanilidovinylbenzothiazole ethiodide, 2.6 g. (1 mol.l100%)methylin dole and cc. of acetic .anhydride were refiuxed 5 minutes. The orange solutionwas chilled; filtered, the dye washed with .acetoneand water and dried. Yield' 1.8 g.; 81%. After Yreorystalli zation from MeOH,` (200 cc./g.) `the product was obtained as minute red crystals with metallic reflex melting with decomposition at 29o-292.

CzHs

4.34 g. (1 mol.) 2-acetanilidovinylbenzoxa- Eole ethiodide, 2.7 g. `(1 mol.+35%) 2hexylindo1e and 15 cc. of acetic anhydridewere refluxed 5 minutes. Dye separated from the boiling solution. Chilled,` ltered, washed with acetone and water and dried. Yield 2.8 g., 56%. After recrystallization from MeOH the product was obtained as minute brown crystals with metallic reflex melting' with decomposition at 272274. Yield 1.4 g., 28%.

EXAMPLE 9 (3-ethy12-benzoxazole) (1,2-dimethyl-3indole) dimethinecyanine iodide .87 g. (l mol.) 1,2-dimethyl-3-indo1ealdehyde, 1.45 g. (l m01.).Z-methylbenzoxazole ethiodide and 10 cc. acetic anhydride were refluxed 5 minutes. Orange coloration. Solid dye separated fromthe boiling reaction mixture. Chilled, -ltered, washed with water and acetone and dried. Yield of brownish yellow crystals 2.15 g.,`97%. After recrystallization from MeOH (50 Cc./g.), the product was obtained as orange crystals melting with decomposition at 264-265". Yield 2.0 g., 90 MeOI-I solution `yellow.

155 phenylpyrrole and25 ccfacetic anhydride were reuxed l-minutes. Theorange mixture was chilled, filtered, product washed with water and acetone anddried. Brown crystals. Yield 2.7 g., 57%. After recrystallization from MeOH (15 60 zc/g.) the dye was obtained as light brown crystals melting with decomposition at 214-220. Yield 1.6 g., 34%. After three further crystal-I lizations from abs. EtOI-I with Norite the M. P. was constantat 249-251`dec. MeOH solution vcyanme iodide 4.34 g. (1 m01.) 2--acetanilidovinylbenzoxazole ethiodide, `3.7 g. (1 mobi-100%) 1-benZyl-2,5 dimethylpyrrole and 15 cc. acetic anhydride were refluXed for 10 minutes. Brownish orange coloration. Chilled, ltered, washed with acetone and Water and dried. Yield of brown crystals 3.1 g., 64%. After recrystallization from abs. EtOH (20 cc./g.) the product was obtained as granular brown crystals melting with decomposition at 21S-221. Yield 2.0 g., 41%. MeOM solution yellow.

EXAMPLE 12 /o \CCH=CH-- \N% M lV'e Et 1 l O-Me (3-ethyl-2-benzoxazole) (1-p-meth0Xy-pheny1-2,E5-dimethyl 3-pyrrole) dimethinecyanine iodide 4.34 g. (1 mol.) 2-acetanilidovinylbenzoxazole ethiodide, 4.0 g. (1 mol.|100%) 2,5-dimethyl-1- p-methoXy-phenylpyrrole and cc. acetic anhydride were refluXed 15 minutes. Orange coloration. Chilled, ltered, washed with acetone and water and dried. Brown crystals. Yield 2.5 g., 50%. After recrystallization from abs. EtOH (11 cc./g.), the product was obtained as granular lbrown crystals melting with decomposition at 214-217". Yield 1.9 g., 38%. yellow.

EXAMPLE 13 Me-\N/-Me l (cetyl and octadecyl mixture) 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 6.4 g. (1 mol.-|100%) mixture of 1 cetyl-2,5-dimethylpyrrole and 1octadecyl-2,5di methylpyrrole and cc. acetic anhydride were reluxed 5 minutes. Chilled, ltered, washed with acetone and water and dried. Brown crystals, Yield 4.1 g., 66%. After recrystallization from abs. EtOI-I (5 cc./g.) the product was obtained as Ibrown needles melting with decomposition at 180-183". Yield 3.7 g., 60%. MeOH solution yellow.

EXAMPLE 14 C-CH=cH-- N ivre-M M N/ e Et I N (Me) z (1-pdimethylaminophany1-2,dimethyl-S-pyrrolw- (S-ethyl-2-benzoxazole)dlmethmecyanme lodlde MeOH solution 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 4.3 g. (1 mol.}100%) 1pdimethyl aminophenyl-2,5dimethyl-pyrrole and 15 cc. acetic anhydride were refluxed 10 minutes. Orange coloration. Chilled, filtered, washed with acetone and water and dried. Yield 4.3 g., 84%. After recrystallizaton from MeOH, (33 cc./g.) the product was obtained as brown crystals with a bright reex melting with decomposition at 264-266". Yield 3.75 g., 74%. MeOH solution yellow.

EXAMPLE 15 s\ %C-CH=CH /N\ Me* N f--Me HOCH2CH2 Br lauryl EXAMPLE 16 (3-ethyl-2-benzoxazole) (Z-phcnyl-l-pyrrocoline) dimethinecyanine iodide 1.93 g. (1 mol.) Z-phenylpyrrocoline, 4.34 g. (1 mol.) 2--acetanilidovinyl-benzoxazole ethiodide and 25 cc. glacial acetic acid were reluxed 10 minutes. Red coloration. Chilled ltered, washed with acetone and water and dried. Yield of red crystals 4.45 g., 91%. After recrystallization from abs. EtOH, (19 cc./g.) the product was obtained as granular red crystals melting with decomposition at 204-205" Yield 3.9 g., 79%. MeOH solution orange.

EXAMPLE 17 C-cH=oH-C N l /N\ CH3-C=OH E1; I

(Ii-ethyl-Z-benzoxazole) (2-methyllpyrrocolinc) dimcthinecyaninc iodide 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxa- Zole ethiodide, 1.3 g. (1 mol.) Z-methylpyrrocoline and l5 cc. glacial acetic acid were reuxed 5 minutes. Red coloration. Chilled, ltered, washed with acetone and water and dried. Yield of green crystals 3.85 g., After recrystallization from MeOH, (39 ca /g.) the dye was obtained as green crystals with a golden reflex melting with decomposition at 2451-246". Yield 3.2 g., 75%. MeOH solution orange.

l CHz-CHz-OMe 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 3.0 g. (1 mol.+100%) 1-/3- methoxyethyl-2,5-dimethylpyrrole and `cc. acetic anhydride were refluxed 10 minutes.` The brownish-yellow mixture was chilled, 105 cc. ether added and again chilled with stirring. The dye which separated was ltered cir, washed with acetone and water and dried. Yield of brown crystals 3.5 g., 77%. After recrystallization from abs. EtOH, (14 cc./g.) the dye was obtained as brown crystals melting with decomposition at 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 3.6 g. (1 mol.-|100%) 2,5-dimethy1-1- tetrahydrofurfurylpyrrole and 25 cc. acetic anhydride were refluxed 10 minutes. Brownish orange coloration. Chilled, filtered, washed with acetone and Water and dried. Yield 3.8 g., 79%. After recrystallization from MeOI-I, (24 cc./g.) the dye was" obtained as brown crystals melting with decomposition at Z50-251. Yield 3.35 g., 70%. MeOHsolution yellow.

EXAMPLE ethiuecyanine iodide 4.34 g. (1 mol.) Z-acetanilidoyinylbenzoxazole ethiodide, 3.54 g; (l mobi-100%) 1`cyclohexyl, 2,5-dimethylpyrrole and 25 cc. acetic anhydride were refluXed 10 minutes. Orange coloration. Chilled, dye pptd with 100 cc. ether, ether decanted off and residue stirred with 10 cc. acetone until crystalline. Filtered, washed with acetone and-water and dried. Yield 2.25 g., 45%. After recrystallizationfrom abs. EtOH, (13 cc./g.) the dyewas obtained as orange needles melting with decomposition at Z50-252. Yield 2.0 g., 42%. MeOH-solution yellow.

EXAMPLE 22 CMG Y dimethinecyanine iodide 4.34 g. (1 mol.) 2--acetanilidovinylbenzoxazole ethiodide, 1.5 g. (1 mol.) 2,3-'dimethylpyrrocoline and 25 cc. glacial acetic acid `were refluxed 5 minutes. Red coloration. Chilled, stirred until crystalline, again chilled and filtered. Washed with acetone and water and dried. Yield of dark red crystals 3.85 g., 87%. A'fter recrystallization from MeOH, (42 cc./g.) the dye was obtained as greenish-red needles with green-reflex meltingr with decomposition at 2651-267". Yield 3.55 g., 80%. MeOH solution orange.

EXAMPLE 23 Me \I Mel lauryl 3.0 g. (1 mol.) 2,3,3-trimethylindolenine meth- `pyrrolealdehyde, 5 drops piperidine and 15 cc.

abs. EtOI-I were reluXed lhour. Orange coloration. Cooled. 3.0 g. (1 mo1.}-100%) NaI in l5 cc. MeOH addedand mixture diluted to cc. with ether. Orangered crystals separated. Chilled, filtered, Washed with ether and water and dried. Yield 3.1 g., 54%. `After recrystallization from abs. EtOH, (8 cc./g.) the dye was obtained as bright `red iakes melting with decomposition at 283-2856". Yield 2.0 g., 35%. MeOH solution orange.`

EXAMPLE`24 indolenine hydrobromide 2.6 grams (1 mol.) 2-(4-acetanilido-1,3-butadienyD-benzothiazole ethiodde, 1.3 grams (1 mol+100%) x-methylindole and 15 cc. acetic anhydride were refluxed minutes. The purple reaction mixture was chilled, the dye which separated iiltered off and washed with Water and acetone. The green crystals of dye were dissolved in 150 cc. hot CHaOI-I, iiltered and solution of excess NaBr in water added. Chilled, product filtered off, washed with acetone and water and dried. Blue crystalline product. Yield .65 gram, 31%. After recrystallizaticn from CHsOl-I, (100 cc./g.) the dye Was obtained as blue crystals melting with decomposition at 269-270". Yield .4 gram, 19%. CHaOH solution red.

EXAMPLE 25 %C-CH=CH-CH=CH-C=\N \N CuHi-'C-:H Et C1 (3-ethyl-2-benzothiazolc)-(2-phenyl-l-pyrrocoline) tetramethine cyanine chloride 4.8 grams (1 mol.) 2-(4acetanilido-1,3buta dienyl) benzothiazoleethiodide, 1.93 grams (1 mol.) Z-phenyl-pyrrocoline and 30 cc. glacial acetic acid were refluxed 3 minutes. Blue coloration and green crystals of dye separated at once from the boiling mixture. Chilled, iiltered, washed with acetone and Water and dried. Yield 2.6 grams, 49%. The product was extracted with 700 cc. boiling CHsOH. Residue of green crystals 1.3 grams, M. P. 257-259". The solution was chilled and yielded .65 gram green needles, M. P. 257-259o side by side with above. Combined yield 37%. The dye was converted to chloride in 50 cc. cresol solution using 100% excess freshly precipitated silver chloride. The mixture was stirred mechanically for minutes at 100, filtered hot and chilled. Diluted to 400 cc. with ether and chilled overnight. The green crystals which separated were filtered off, washed With ether and acetone and dried. Yield 1.6 grams, 36%. After recrystallization from absolute EtOH, (l5 cc./g.) the product was obtained as green needles with bronze reflex melting at 85- 86, yield 1.3 grams, 30%. CHsOI-I solution bluish-red.

EXAMPLE 26 (3-ethyl-2-benzoxazole)(2-methyllpyrrocoline)-tetramethinecyanine iodide CHaC=JJH 4.6 grams (l mol.) 2-(4acetanilido1,3buta dienyl) benzoxazole ethiodide, 1.3 grams (1 mol.) Z-methyl-pyrrocoline and 30 cc. glacial acetic acid Were reiluXed 5 minutes. Blue coloration. Green crystals separated at once from the boiling mixture. Yield 2.9 grams, 64%. Dissolved in 50 cc. cresol (m and p mixture) heated to 125, ltered hot, cooled and diluted With 250 cc. CHsOI-I. Green crystals separated on chilling. Filtered, Washed With CHsOH and dried. Yield 1.95 grams, 43%, M. P. 247-250" dec. CHsOH solution blue.

(B-ethyl-Z-benzothiazole (2,3dimethyl1pyrrocoline) tetra-methinecyanine-p-toluenesulfonate 4.9 grams (1 mol.) 2(4acetanilido-1,3buta dienyl) benzothiazole-etho p toluenesulfonate, 1.45 grams (1 mol.) 2,3-dimethylpyrrocoline and 25 cc. glacial acetic acid were reuXed 5. The blue solution was cooled, diluted with 50 cc. acetone and cc. ether and chilled. The dye which separated Was filtered oi, washed with ether, acetone and Water and dried. Yield of green crystals, 2.3 grams, 43%. After recrystallization from MeOH (32 cc./g.) the product was obtained as bright green crystals melting with decomposition at 272-273". Yield A2.0 g., 38%. Solution blue in MeOH.

EXAMPLE 28 3-[l-ethyl-2(l)--naphthothiazolylidenc)ethylidene]2 methylindolenine hydrochloride 3.5 grams (1 mol) of 2-methyl--naphthothiazole ethiodide, 1.6 grams (l mol) of 2-methyl- 3-indolealdehyde, 3 drops piperidine and 25 cc. of absolute ethyl alcohol were refluxed for 30 minutes. Orange coloration. Dye separated slowly from the boiling mixture. Chilled, ltered, Washed with Water and acetone and the red crystalline product boiled up with 100 cc. of hot Water to remove colorless crystals of unchanged Quaternary salt, Filtered hot, Washed with Water and dried. Yield 1.1 grams, 22%. The dye Was converted to the chloride by treatment with eX- cess freshly precipitated silver chloride in cresol. The crude chloride was obtained as red crystals. Yield 6 grams, 15%. After recrystallization from absolute ethyl alcohol (300 cc./g.) the product was obtained as dull red crystals melting with decomposition at 258-260". Yield .3 gram, 8%. Methyl alcohol solution orange.

EXAMPLE 29 3[ (3-lauryl-2 3) -benzothiazolylidene) ethylldene] -2- methyl-indolenine hydro-iodide 2.95 grams (1 mol) Z--acetanilidovinylbenzothiazole laur-iodide, 2.6 grams,(1 mol and 300%) a-methylindole and 15 cc. acetic anhydride were reuxed 10 minutes. rIhe reddish orange mixture was chilled, ltered, Washed WithV acetone and water and dried. Dark green crystals. Yield 2.6 grams, 89%. After recrystallization from methyl alcohol (31 cc./g.) the product was obtained as granular green crystals melting with decomposi- 13 tion at 21g-220. Yield 1.3 grams, 44%. Methyl alcohol solution yellow.

In the present specification we refer to dyes containing a pyrrole nucleus. It is to be understood that by this term we intend to include dyes derived from both pyrrole and indole, the indole nucleus being considered a substituted pyrrole, and the term pyrrole nucleus being generic to both pyrrole and indole. While we refer in the claims to dyes containing a pyrrole nucleus, we intend to include both pyrrole and indole dyes.

For the preparation of overcoating layers, filter layers and anti-halation layers, according to our invention, from 50 mg. to 150 mg. of dye are dissolved in from 2 to 5 cc. of a Water-miscible solvent. Methanol or acetone are suitable for this purpose but pyridine or Cellosolve may also be used. The solution is then added to about 25 cc. of a gelatin solution at 40 C. and the mixture coated on the support. If the dye is too insoluble as the iodide salt it may conveniently be converted into the chloride, using cresol as a solvent for the conversion.

In the accompanying drawing, the various iigures are enlarged section views of photographic elements having lter layers and anti-halation layers madev according to our invention. As shown in Fig. 1 a support I0 of any suitable material such as cellulose nitrate or cellulose acetate, synthetic resinous material, or opaque material such as paper is coated with an emulsion layer I I and an overcoating layer I2 containing a pyrrole polymethine dye according to our invention.

Fig. 2 illustrates a multi-layer photographic element for color photography in which the support IB is coated with sensitive layers I3, I4 and It which record respectively the red, green and blue regions of the spectrum. Between the emulsion layers I3 and Ill, there is a lter layer I6 containing a red pyrrole polymethine dye and between the layers I4 and I5 there is a layer Il containing a yellow pyrrole polyrnethine dye. These lter layers serve purposes Well known in color photography of preventing exposure of a lower layer of the element by light which the lter layers absorb. The pyrrole polymethine dyes used may also absorb light in other regions, such as ultra-violet light.

Fig. 3 represents a iilm having an anti-hala- Ition layer containing a pyrrole polymethine dye according to our invention. As shown therein, the support I contains an emulsion layer II on one side and ananti-halatlon layer I8 containing the pyrrole dye on the opposite side.

Our invention is not limited to the examples included in the present specication but any compounds coming within the scope of the invention may be used. The dyes may be dispersed in gelatin, collodion, gum arabic, synthetic resins or other suitable colloid or they may be dispersed in photographic emulsions such as gelatino silver halide emulsions and may be coated in any suitable manner. l

It is to be understood that our invention is limited only by the scope of the appended claims.

We claim:

l. A compound having the following general formula:

R."=a substituent selected from the group consisting of hydrogen, alkyl and aryl Xzan acid radical Y=a substituent selected from the group consisting of O, S, and -CH=CH d=a positive integer of from 2 to 3.

2. A compound having the following general where R is selected from the class consisting of octadecyl and cetyl radicals.

LESLIE G. S. BROOKER. ROBERT H. SPRAGUE. 

